Isolation of a Thermophilic Bacterium Producing a Thermostable a-Glucosidase and Characterization of the Enzyme

Lee, Yong-Eok 동국대학교 생명과학연구소 1995 생명과학연구논문집 Vol.2 No.-

A thermophilic bacterium producing a thermostable α-glucosidase was isolated from manure and as been identified as Bacillus sp. The optimum temperature for growth was 65°C. No growthwas obtained at 40 or 75°C. The optimum pH for growth was 5.5 to 8.5. The α-glucosidase production was constitutive in the absence of carbohydrates. High level of enzyme activity was detected during growth in starch. Addition of glucose resulted in the repression of the α-glucosidase production. The optimum pH and temperature for enzyme activity were pH 4.8 to 5.0 and 60 to 65°C, respectively.

Ligand Binding Assays with Recombinant Proteins Refolded on an Affinity Matrix

Yoon, Joo-Ok 동국대학교 생명과학연구소 1994 생명과학연구논문집 Vol.1 No.-

This paper describes a procedure for performing ligand binding assays with recombinant proteins or protein fragments that can bind to an affinity matrix in the presence or absence of a denaturing agent but which require the presence of the denaturing agent to remain in solution. The method involves coupling of a known amount of the protein in a denaturing medium to a known amount of the affinity matrix, replacing the denaturing agent with a physiological buffer, and finally using the suspension of this protein-couple matrix as the source of the recombinant protein to be studied for its functional properties. A constant volume of this suspension is incubated with different concentrations of a radiolabeled ligand. Radioactivity bound to the protein-coupled affinity matrix is determined after centrifugation and washing of the pellet. Nonspecific binding is determined either by using the uncoupled affinity matrix or by the standard technique of measuring the binding in the presence of excess unlabeled ligand.

Protein Folding-What's the Question ?

Yoon, Joo-Ok,Noh, Wan Seob 동국대학교 생명과학연구소 1994 생명과학연구논문집 Vol.1 No.-

The folding reactions of many small, globular proteins exhibit two-state kinetics, in which the folded and unfolded states interconvert readily without observable intermediates. Typically, the free energy difference, △G, between the native and denatured states of sch a protein is quite small, lying in the range of approximately -5 to -15 kcal/mol. We point out that, under these circumstances, a population of native-like molecules will persist, even in the presence of mutation sufficiently destabilizing to change the sign of △G. Therefore, it is not energy per se that determines conformation. A corollary to this argument is that specificity - not stability - would be the more informative focus in future folding studies.

Purification of a Pepstatin-Insensitive Carboxyl Proteinase from Lampteromyces japonicus

Yoon, Joo-Ok 동국대학교 생명과학연구소 1995 생명과학연구논문집 Vol.2 No.-

A carboxyl proteinase was purified from Lampteromyces japonicus. The optimum pH of the purified enzyme was 3.2 and its caseinolytic activity was not inhibited by carboxyl proteinase inhibitors, such as diazoacetyl-DL-norleucine methyl ester and pepstatin. 1,2-epoxy-3-(p-nitrophenoxy) propane modified the enzyme with concomitant loss of its enzyme activity. The enzymatic properties of the enzme were compared with those of known pepstatin-and diazoacetyl-DL-norleucine methyl ester-insensitive carboxyl proteinases previously reported.

Ribosomes Isolated from T. novellus Grown under Different Cultural Conditions

Park, In Kook,Jung, Heon Keun,Shin, Sook 동국대학교 생명과학연구소 1994 생명과학연구논문집 Vol.1 No.-

The growth rate and sedimentation profile of ribosomes of T. novellus under autotrophic and heterotrophic conditions were investigated. When T. novellus was grown autotrophically, the growth proceeded at a slow rate characteristic of autotrophs and did not enter log phase until the end of the first day. Logarithmic growth proceeded for 3-4 days at which time the cells entered the stationary phase and was accompanied by decreasing pH culture media. In heterotrophic media the growth proceeded at a much faster rate and cells entered stationary phase 20-22h after inoculation. The sedimentation profiles of heterotrophic ribosomes reveal that the incomplete dissociation occurred at 10mM and 5 mM Mg^(2+) concentrations whereas almost complete dissociation of ribosome was observed at 1mM Mg^(2+) concentration. In the case of autotrophic ribosomes, at 10 mM Mg^(2+) only a single 50s peak was observed but at lower Mg concentration such as 5 mM and 1 mM the amount of 30s peak increased progressively. Even at lower Mg^(2+) level, autotrophic ribosomes were not fully dissociated as compared to heterotrophic ribosomes.

Differential Characteristics of Genus Campylobacter and Related Bacteria

Han, Yeong-Hwan 동국대학교 생명과학연구소 1994 생명과학연구논문집 Vol.1 No.-

Using 16S rRNA nucleotides sequence analyses, genus Campylobacter and related microorganisms can be classified into four genera (Campylobacter, Wolinella, Helicobacter, and Arcobacter). So far, it has been very difficult to classify these micoorganisms with phenotypes, because the organisms can not utilize carbohydrates as carbon and energy sources for their growth. For determining the characteristivces to easily differentiate these organisms on the level of genus, physiological (growth in the presence of 1.0% bacto-oxgall, 1.0% glycine, 3.5% NaCl and citrate utilization) and biochmical (activities of aminopeptidase, alkaline phsphatase, amino acid decarboxylase, and APIZYM) tests were carried out. The phenotypic characteristics tested in this study and other results published elsewhere might be used for the classification of the organisms.

생분해성 폴리펩티드-폴리에스터를 포함하는 블록공중합체의 합성 및 물성에 관한 연구

성용길,송대경,성정석 동국대학교 생명과학연구소 1994 생명과학연구논문집 Vol.1 No.-

Poly(L-lacticacid-co-glycine-L-lactic acid),poly(L-lactic acid-co-glycine-L-methyl-lactic acid), and poly(glycolic acid-co-glycine-L-lactic acid) have been synthes-ized by ring opening polymerization. L-Lactide, glycolide, and 6-methyl morpholine-2,5-dione were used as starting materials for the biodegradable polyester-polypeptide block copolymers. The synthesized block copolymers have been identified by FTIR and NMR, and characterized by DSC and TGA. The glass transition temperatures of poly(L-lactic acid-co-glycine-L-lactic acid) are higher than those of poly(L-lactic acid) and poly(glycolic acid-co-glycine-L-Lactic acid) respectively. The glass transition temperature of poly(L-lactic acid-co-glycine-L-lactic acid) is lower than that of poly(L-lactic acid-co-glycind-L-Methyl-lactic acid), showing thyat its segmental motion is decreased by methyl group. The thermal degradations of those polyester-polypeptides are decreased by increasing of the mole fraction of 6-methyl morpholine-2,5-dione.

Thymidylate Synthase Activity in Mutants by site-Directed Mutagenesis

Park, In Kook,Shin, Sook 동국대학교 생명과학연구소 1994 생명과학연구논문집 Vol.1 No.-

In vitro oligodeoxyribonucleotide-directed mutagenesis was employed to delineate the structural importance of P1 and P2 in the 5' region of the td intron. When a U.G pair was changed to a U.C par in the 5'splice site of P1 stem of td intron, the activity of thymidylate synthase in vivo was totally lost whereas the wild type retained the normal activity. The enzyme activity was about 32 % of that of the wild type when U at 12 position was changed to C. The deletion of P2 led to a complete loss of the enzyme activity. A very similar loss of enzyme activity was observed with substitutions at 5'end(U18G) and at 3'end(A29C) of P2 stem. however, a compensatory double mutation(U18G/A29C) restored 52% of that of wild type enzyme activity. The results suggest that the maintenance of the intact Pl and P2 structure is an essential requirement for splicing of td gene in vivo.

실험동물의 서로 다른 기관에 함유되어 있는 Hydroxyproline 측정에 관한 연구

한애란,김기영,민태진 동국대학교 생명과학연구소 1994 생명과학연구논문집 Vol.1 No.-

Conformational Entropy of Amino Acid Side Chain in Protein Folding

Yoon, Joo-Ok 동국대학교 생명과학연구소 1995 생명과학연구논문집 Vol.2 No.-

An important contribution to the thermodynamics of protein folding is the loss of entropy that results from restricting the number of accessible side chain conformers in the native structure. Conformational entropy changes can be found by comparing the number of accessible rotamers in the unfolded and folded states, or by extimatingfusion entropies. Comparison of several sets of results using different techniques shows that the mean conformational free energy change (T△S) is 1 kcal·mol^(-1) per side chain or 0.5 kcal·mol^(-1) per bond. Changes in vibrational entropy appear to be negligible compared to the entropy change resulting from the loss of accessible rotamers. Side chain entropies can help rationalize α-helix propensities, predict protein / inhibitor complex structures, and account for the distribution of side chains on the protein surface or interior.